opencv车牌识别python代码

以下是基于OpenCV实现的Python代码，用于识别车牌。

import cv2
import numpy as np

# 读取图片
img = cv2.imread('car.jpg')

# 将图片转为灰度图
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# 高斯滤波
blur = cv2.GaussianBlur(gray, (5, 5), 0)

# 边缘检测
edges = cv2.Canny(blur, 50, 200)

# 膨胀操作
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (5, 5))
dilate = cv2.dilate(edges, kernel)

# 查找轮廓
contours, hierarchy = cv2.findContours(dilate, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)

# 查找矩形轮廓
rects = []
for cnt in contours:
    x, y, w, h = cv2.boundingRect(cnt)
    area = cv2.contourArea(cnt)
    if area > 500 and w > h:
        rects.append((x, y, w, h))

# 对矩形轮廓进行排序
rects = sorted(rects, key=lambda x: x[0])

# 识别车牌号码
plate = ''
for rect in rects:
    x, y, w, h = rect
    roi = gray[y:y+h, x:x+w]
    th = cv2.threshold(roi, 0, 255, cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]
    text = pytesseract.image_to_string(th, config='--psm 7')
    plate += text

# 显示识别结果
print('车牌号码：', plate)

cv2.imshow('img', img)
cv2.imshow('edges', edges)
cv2.imshow('dilate', dilate)
cv2.waitKey(0)
cv2.destroyAllWindows()

需要注意的是，这段代码中使用了OCR（Optical Character Recognition，光学字符识别）技术来识别车牌号码，需要安装tesseract-ocr和pytesseract库。在安装完这两个库后，需要将pytesseract.image_to_string()函数的config参数设置为'--psm 7'，这样才能正确识别车牌号码。